Cook sushi rice as instructed. Slice avocado into thin slices. The green beans don't have to be cut, but you can do so if you wish.
Stir 1/2 tablespoon rice vinegar into prepared sushi rice. Shape into a ball, then spread over nori. Lay avocado slices and green beans in a row. Roll and seal by dipping fingers in water/rice vinegar combo and pressing closed; dampen entire roll for easier cutting. Slice, and enjoy.